1. Field
This disclosure relates generally to a switching control circuit, and more particularly to driving a switching control circuit for a lighting apparatus.
2. Description of Related Art
Some power factor correction converters operate in a continuous conduction mode and a boundary conduction mode. In the continuous conduction mode, a fixed frequency is used to control an inductor current (or a driving current). In the boundary conduction mode, a variable frequency signal is used to turn on a driving switch when the inductor current reaches a zero.
A light emitting diode (LED) lighting apparatus may be driven by a switching converter, of which types include a buck-type, a boost-type, and a buck-boost-type. The boost-type switching converter has been commonly used, but recently the buck-type switching converter has also become popular for being implementable in an integrated circuit (IC) in a cost effective manner. The switching converters may be classified by the ratio between an input voltage and an output voltage, and may include a metal-oxide-semiconductor field-effect transistor (MOSFET) in order to implement an average inductor current mode method.
In operation, the switching converters use a drain voltage of the MOSFET to detect when the inductor current becomes zero. The drain voltage of the MOSFET decreases when the inductor current becomes zero. To detect this, the IC is typically implemented with costly elements that drive up manufacturing costs.